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Cold weather and the Prius skeptic

Prius cold weather performance has been the straw most often grasped by hybrid skeptics. The 1.5L Prius take pains to minimize emissions and engine warm-up and this burns more gas, often inefficiently. Worse, at high power settings, the 1.5L engine uses fuel enrichment to avoid burning out the catalytic converter. It didn't take long for petroleum addicts, petrodicts, to decide this would be their 'hook' for Prius critical articles.

The first I remember was a Car and Driver article that decided the middle of winter was the perfect time to do a highway, comparison drive between a Prius and Jetta diesel. A more blatant effort was the "Green Human" Portland-to-Portland, 8,000 mile, cross-country USA drive between a 1.5L Prius and Jetta diesel. But in the end, there was only a 0.5 MPG difference between the larger, roomier Prius and the compact Jetta. Even now, hybrid skeptics trot out the 10 F blizzard on the highway as their metric for Prius performance as if that is the only metric that counts.

Now the 1.8L Prius introduced two technologies that directly address cold-weather and high-power performance:

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image shows the collant pipe from the exhaust heat exchanger. Soinstead of de-tuning the engine to accelerate engine warm-up, thewaste heat downstream of the catalytic converter is captured and sentto the engine block. A by-product is during winter operation, thisformerly waste heat preserves both the engine block heat and providesexcellent cabin heat. The second technology is:
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image shows the 5th tube on the exhaust manifold that routesexhaust gas to a cooler before it feeds into the intake manifold.Cooled, exhaust gas recirculation means at high power settings, thisinert gas cools the exhaust to protect the catalytic converter. Theengine does not have to run an over-rich mixture. Effectively, thesetwo technologies have eliminated the 10F blizzard from the petrodictscriticism . . . except for those still thinking the 1.5L Prius is theonly benchmark. But there is one area that the 1.8L Prius needs tofurther improve high-speed and cold weather performance. One of the earliest owner mods is to block the radiator air inlet. This reduces cooling drag, improves warm-up, and reduces vehicle drag. The Chevy Cruz Eco uses variable vanes and in Japan, Prius owners can buy an after-market, variable air inlet kit. With the return of Fall weather, I've put my duct tape wrapped, pool noodle back in my 1.5L,

2003 Prius to preserve summer mileage. By careful measurements last winter, there was a 5% improvement in mileage using a whole, air-inlet block in my wife's 1.8L Prius.

About three years ago, we had a record setting, cold air system come to Dixie when I needed to drive to South Carolina to buy a failed traction battery. The high pressure center was over Atlanta, midway in my trip. I left at 4:00 AM, 15F and by the time I reached Atlanta, it had not reached freezing. It wasn't until 2:00 PM when the temperature finally reached 37-38F. I picked up the traction battery and by the time I returned home at midnight, it was back to 18F.

I kept my speed constant 65 mph on the highway and measured the mileage over different temperature ranges only to find later that the mileage followed the air density as a function of temperature. The highest milege was 49-50 MPG at 37-38F and 65 mph. Other segments were down as low as 34-35 MPG solely due to the higher air density of cold air.

The 1.8L Prius could be improved with variable, cooling air inlet vanes. But compared to the 1.5L Prius, it is substantially improved with exhaust warmed coolant and cooled exhaust gas recirculation. We see this in the average mileage owners report for the 1.8L Prius over the earlier 1.5L Prius. Petrodicts are left with crying over the 1.5L Prius in a 10F blizzard.

Bob Wilson

Reply to
bwilson4web
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Does thin skin run in the family?

Reply to
News

you know, because actual facts--like my observed fuel economy this past winter--are immaterial to people like you.

Reply to
Elmo P. Shagnasty

Which leads to some questions, such as:

  • why didn't Toyota engineer this as a standard feature?
  • can/will Toyota use this "owner mod" as a reason to void any warranty claims?
Reply to
Elmo P. Shagnasty

Well, my posting seems to have woken some folks up:

Facts and data often drive hybrid skeptics into ad hominen postings. So collecting the more recent 'skeptic' laments in one thread is an effective technique.

As my first posting shows and other studies not yet cited, I do study Prius cold weather performance. For example, my earliest transaxle oil testing:

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I use metrics to obtain facts and data as there is a big difference between "anedotal" reports and an engineering analysis with hard data. The former often come across as whining whereas a reasoned, disciplined study can provide insights to mitigate a problem. When someone is in darkest ignorance, I'm not one to complain, much, but rather prefer to "light a candle" and learn something useful.

I have no idea but that that is not unique to Toyota. There is a huge, after-market for just about every vehicle that has ever been made ranging from turbo-chargers to anything that can be bought and installed on or in a car. The generic version of this boring question is:

"Why didn't [any manufacturer] engineer this as a standard feature?"

They didn't so owners and enthusiasts fill in the answer and are thankful for the business opportunity.

I was concerned about this so when I bought my 2003 Prius with 49,000 miles, I held off on any changes that might impact the 60,000 and

100,000 mile warranties. But adding a 1 kW inverter did not touch these other systems and was my first modification. Once my car passed those later milestones, I was free to make any modification I wanted. So last November, I upgraded my traction battery to NHW20 style modules.

A warranty has value and I would recommend anyone wishing to make or test a modification to be very cautious until the warranty period is over. For example, my wife's 2010 Prius bought in May 2009 has the

3/36000 warranty until June 2012 or about nine months to go. Once her car passes that threshold, I'll put in the 1.5 kW inverter and may upgrade her 12V battery. Other modification will wait until the drive train warranty, 6/60000 and traction battery/inverter warranty, 10/100000 have passed.

Bob Wilson

Reply to
bwilson4web

So, what do the FACTS of 35mpg do for YOU?

Oh, that's right--you ignore THOSE facts, because they're inconvenient for you.

Reply to
Elmo P. Shagnasty

In other words, the fact that people individually report that "cold weather makes a HUGE hit on mileage" is to be completely ignored by you.

Got it.

Reply to
Elmo P. Shagnasty

So, what do the FACTS of 35mpg do for YOU?

Oh, that's right--you ignore THOSE facts, because they're inconvenient for you.

You 35 mpg may be fact to you, but it is unsubstantiated hearsay to me. Call me a skeptic, but I've not seen cold weather mileage like that and I believe I've driven in some of the coldest weather in the 49 of the 50 states.

Reply to
Al Falfa

In other words, the fact that people individually report that "cold weather makes a HUGE hit on mileage" is to be completely ignored by you.

Got it.

Again, it makes a small difference, perhaps 5%, in temperature extremes ranging from 100F to -30F. I notice that you have taken the headwind out of your recent statements regarding cold weather performance. So much for "fact" Elmo.

Reply to
Al Falfa

I don't agree with the troll about 35mpg, but it's more like a 10% drop for us in Winter in the Northeast. I hope to cut that in half by partially blocking off the grille, but that's modifying the car.

Reply to
Leftie

2010. I have cardiovascular disease, and the sporadic nature of the hot air at floor level is a problem.
Reply to
Leftie

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